About 1833, through meeting Adam Sedgwick at Barmouth and joining him in several excursions, Hopkins became intensely interested in geology. From then on, in papers published by the Cambridge Philosophical Society and the Geological Society of London, he defined the discipline of physical geology, making mathematical investigations dealing with the effects that an elevatory force, acting from below, would produce on a portion of the Earth's crust, in fissures and faults. In this way he discussed the elevation and denudation of the Lake District, the Wealden area, and the Bas Boulonnais.